Write a simple program to play a game of Tic-Tac-Toe.
The game is between two players.
The computer starts displaying the board with all the empty spots and asks for the first move.
A B C
1 _|_|_
2 _|_|_
3 | |
The computer asks each player for their move:
- the player will inform the coordinates to place her mark with a letter and a number
- the letter indicating the column and the number the row.
The computer will keep asking both player for their marks until one of them win or there are no more places in the board to position marks.